Reactive fluids, such as sub-critical, near-critical, and/or supercritical fluids, are highly energetic fluids having a high temperature and high pressure. These reactive fluids can be used to treat materials comprising polymers and/or oligomers to decrease the degree of polymerization or oligomerization of the polymers or oligomers in the material. For example, biomass, which typically is composed of natural polymers or oligomers, such as cellulose, hemicellulose, and lignin, or waste feedstocks, which may contain natural or synthetic polymers or oligomers, can be hydrolyzed by treatment with sub-critical, near-critical, and/or supercritical water to produce monomers and/or shorter chain polymers and oligomers.
Generating reactive fluids having a high temperature and high pressure is an energy intensive process. Without effective management of the system, the heat and pressure associated with the reactive fluid will dissipate into the ambient environment during or after treatment of a material, thereby losing the energy associated therewith. To economically operate a system that employs reactive fluids, an energy recovery system may be employed. Although some energy recovery methods and systems are known, not all recovery methods or systems are applicable to systems that employ reactive fluids. Moreover, it is not obvious which methods or systems should be employed to recover energy from processes that treat biomass or waste feedstocks, or how this recovered energy should be redeployed in the energy-originating method or system, or in other co-located or nearby methods or systems. For example, if heat that is recovered from a reactive fluid is not properly reintegrated into the process, undesirable reactions may occur or desirable reactions may not occur at all. Thus, there remains a need in the art for improved methods and systems for recovering and reusing energy when processing materials with reactive fluids.